Water Boiling Point Under Pressure Calculator

Clausius-Clapeyron Equation:

\[ T_b = \frac{1}{\frac{1}{T_0} - \frac{R}{\Delta H_{vap}} \ln \left( \frac{P}{P_0} \right)} \]

Pressure (P):

Reference Temperature (T₀):

Reference Pressure (P₀):

Enthalpy of Vaporization (ΔH_vap):

J/mol

Boiling Point (T_b):

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1. What is the Clausius-Clapeyron Equation?

The Clausius-Clapeyron equation describes the relationship between pressure and temperature at which a substance changes phase between liquid and gas. It provides a way to calculate the boiling point of a liquid at different pressures.

2. How Does the Calculator Work?

The calculator uses the Clausius-Clapeyron equation:

\[ T_b = \frac{1}{\frac{1}{T_0} - \frac{R}{\Delta H_{vap}} \ln \left( \frac{P}{P_0} \right)} \]

Where:

\( T_b \) — Boiling point at pressure P (K)
\( T_0 \) — Reference boiling point (373.15 K at 1 atm)
\( R \) — Gas constant (8.314 J/mol·K)
\( \Delta H_{vap} \) — Enthalpy of vaporization (40650 J/mol for water)
\( P \) — Pressure (Pa)
\( P_0 \) — Standard pressure (101325 Pa)

Explanation: The equation accounts for how boiling temperature changes with pressure based on the thermodynamic properties of the substance.

3. Importance of Boiling Point Calculation

Details: Accurate boiling point calculation is crucial for various industrial processes, cooking applications, scientific experiments, and engineering designs where pressure conditions differ from standard atmospheric pressure.

4. Using the Calculator

Tips: Enter pressure in Pascals, reference temperature in Kelvin, reference pressure in Pascals, and enthalpy of vaporization in J/mol. All values must be positive and valid.

5. Frequently Asked Questions (FAQ)

Q1: Why does boiling point change with pressure?
A: Higher pressure requires more energy for liquid molecules to escape into the gas phase, thus increasing the boiling point. Lower pressure decreases the boiling point.

Q2: What is the default enthalpy of vaporization value?
A: The default value of 40650 J/mol is for water at standard conditions. This value may vary slightly with temperature.

Q3: Can this calculator be used for other liquids?
A: Yes, but you need to provide the appropriate enthalpy of vaporization and reference values for the specific liquid.

Q4: What are the limitations of this equation?
A: The equation assumes constant enthalpy of vaporization and ideal gas behavior, which may not hold perfectly over large temperature ranges.

Q5: Why use Kelvin instead of Celsius?
A: Thermodynamic equations require absolute temperature scales (Kelvin) because they involve ratios and logarithmic functions of temperature.